In the knit textile industry, fabrics are produced in tubular form, which fabrics are worked on while in a string configuration or the fabrics are worked on in open width. That is, in the open width the fabrics are contacted on the flattened fabric tube until its walls are joined together among themselves and expanded to the limit allowed by its elasticity, in the condition that the fabric is in, whether dry or wet, according to the maker or client specific needs. Such a process, for example, is known as calendering, when the fabric is pressed between revolving cylinders.
Many types of expanders are well-known, such as:
a) traditional old and primitive expanders, like those that consist of a wooden mold, of which the width is equal to that width, which one wants to give to the fabric, which is put into the fabric tube, adjacent to the revolving cylinders that pull the fabric through; PA1 b) Types which consist of a pair of rings placed at a distance. Each ring is put into the fabric tube and kept at the desired distance through a pair of wheels placed in V-shaped configuration on the external side of the tube and against an internal surface of the corresponding ring, so that the fabric, which is pulled by the conveyor cylinders, will be located between the internal rings and external wheels; PA1 c) More modern expander types, which are still in use, which consist of two metallic molds put inside of a fabric tube. The molds are properly placed at a distance through an adjustable distance device, and each mold has a pair of internal wheels that oppose and rotate opposite to each internal wheel of a pair of external control and support wheels. The molds may have auxiliary belts for the transportation of the fabric as shown in FIG. 1; PA1 d) and at last, the request document of European patent No. 87830320.5 describes an expander which is proper for dry fabrics, which has the characteristics of not having the distance separator device of the two metallic molds inside the fabric tube. This prior art fabric expander has placed at a distance along the external sides of each mold two pairs of external-internal wheel and belt assembly groups, each group with a driven wheel having an internal convex edge, driven by a motor wheel having an external concave edge and which is supported by two external wheels placed in a V-shaped configuration against its external sides, so that both molds are supported in the desired position during the fabric expansion operation. An internal belt spins around wheels placed along the mold and follows the fabric in its movement as shown in FIG. 2. PA1 a) sensibly in medium position, along its longitudinal extension, at least one first driven wheel, which wheel has a perimeter in the shape of two open wings which form a first concave opening at the botton of which opening there is a second opening having a V shaped configuration, in which is received a first conveyor belt having a reciprocal V shape configuration for the fabric transportation. (For purposes of clarity, each such driven wheel has a perimeter which shows in cross section, opposite pairs of outwardly extending wings, so that when viewed in cross section, the first driven wheel bears an "X" shaped configuration at its side ends, when viewed in cross section, as in FIG. 6 herein. For simplicity the driven wheel will be referred to herein as a "wheel in X"). PA1 b) on the previous and posterior parts of such "wheel in X," at least one second driven wheel having an opening in a V shape configuration in which V-shaped opening is received the first conveyor belt in a reciprocal V shaped configuration, when viewed in cross-section, which stays linked on the "V" shaped openings of the aforesaid "wheel in X" and of the aforesaid second driven wheels. The first conveyor belt stays closed over such wheels, to spin around with them when the "wheel in X" is set into movement and to be in contact with the fabric, which fabric is pressured against it by two wheels of the second external wheel and belt assembly group to transport it to a desired direction. Furthermore, each one of such second external wheel and belt assembly groups include: PA1 c) at least one motor wheel driven by a conventional motor element that has a convex perimeter which fits pressured inside the concave perimeter of the aforesaid "wheel in X", which has at least one concentric fixed pulley, which pulley is linked to a transmission belt that transmits the movement to: PA1 d) at least one balancing driven wheel, on the previous or posterior part of such driven wheel, elastically kept fastened with the convex perimeter inside the concave perimeter of the "wheel in X" and against the first V-shaped conveyor belt, and that has a concentric fixed pulley in which such transmission belt is linked to; PA1 e) a pair of conducting counter wheels moved by such belt, and that has a concentric fixed pulley in which such transmission belt is linked to; PA1 f) a pair of conducting counter wheels moved by such transmission belt. Each one of the counter wheels applies pressure with a wide edge against the external surface of the open wings of such "wheel in X", through the interposed fabric, the same wheels, to keep conveniently distant the relative plate by the opposite plate inside the fabric tube and to transport it to the desired direction and width.
The prior art fabric expanders "a)" and "b)" above noted present the inconvenience of having an operation which is not accurate and which is not reliable enough. The prior art fabric expanders "c)" and "d)" above noted have the inconvenience of being heavy and large, and these expanders may damage the fabric because of the great number of wheels in contact with the fabric.